Robert W. Cox, 67, a former chairman of the Arlington County Board and a retired director of administration at the National Foundation on the Arts and Humanities, died of cardiopulmonary failure Feb. 14 at Northern Virginia Doctors Hospital.

Mr. Cox was elected to the Arlington Board in 1949 and became its chairman in 1952. Shortly thereafter, he and two other board members were forced to resign because of a Virginia law that prohibited federal employes from serving on county boards.

He remained active in local affairs and from 1962 to 1964 was president of the Arlington County Civic Federation. He also was president of the Northern Virginia T.B. Association.

Mr. Cox, who lived in Arlington, was born in Warren County, Va. He attended Shepherd College and earned bachelor's and master's degrees from Syracuse University. He worked briefly for New York State and in 1940 returned to this area to begin his career with the federal government.

He joined the old Bureau of the Budget and remained there until 1949, when he joined the Federal Communications Commission. He became executive officer of the FCC in 1950. In 1963, he transferred to the old Department of Health, Education and Welfare, where he was an operations analyst. He went to the National Foundation on the Arts and Humanities in 1966 and retired in 1967. He was a consultant with Executive Management Services, Inc. until his second retirement in 1975.

In 1949, Mr. Cox received the Star Trophy for distinguished service to the community.

His wife, Ruth O'Dell Cox, died in 1979.

Survivors include three children, Susan Cox Burke and Kevin O'Dell Cox, both of Arlington, and Robert Alan Cox of Bedford, Tex., a sister, Dorothy Cox Dudrow of Ormond Beach, Fla., and nine grandchildren.